Various devices or equipment have heretofore been employed in an attempt to maintain fishing holes free of icing but insofar as known none are presently available for purchase.
A number of Patents have been issued directed to different devices for the above purpose, such as for example, Patents respectively issued to Lewis L. Rydeen, U.S. Pat. No. 3,204,630 dated Sept. 7, 1965, and Henry O. Boklep, No. 2,541,328 issued Feb. 13, 1951, which among other things, disclose tubular hollow walled structures which are located substantially within the confines of a hole in a layer of ice and an appreciable distance therebelow, with gas connections for introducing gas or locating oil heaters in the wall structure.
Another Patent issued to Lloyd O. Paulsen et al, U.S. Pat. No. 2,774,856 on Dec. 18, 1956 shows an annular tubular floatable member containing an electrical heating element.
Also, a Patent issued to Arman W. Holm et al, U.S. Pat. No. 2,747,569 on May 29, 1956 depicts, among other things, a generally crescent shaped receptacle, containing combustible material, which is adapted for placement on a layer of ice with a flange of the receptacle depending into a hole for heating the water when the receptacle is sufficiently hot to transmit heat to the flange.
Further, a Patent issued to Russell E. Obernolte U.S. Pat. No. 2,883,784 dated Apr. 28, 1959 discloses, among other things, a combination of a hollow dome adapted for mounting on a layer of ice over a hole and a buoyant cup candle holder located in an enlarged area of the hole adjacent an inner periphery of the dome.
An additional Patent No. 3,407,283 issued to Harry L. Peterson on Oct. 22, 1968 discloses a bouyant hollow cylinder dependent in one side of an ice hole for receiving heat from a gas burner or electrical element.
The Patents, above referred to, clearly indicate that attempts have been made to maintain fishing holes clear of ice but the foregoing and others directed to the subject appear to be impractical, condusive to probable line entanglement or burning thereof, expensive to manufacture and maintain, and unstable due to their buoyancy and shifting as a result of melting the ice about the hole.